Friday, February 28, 2014

Researchers from ETH Zurich and the University of Tubingen describe a process that suppresses the formation of methane in soils that are rich in humic substances. For this process to work, the soils need to switch between having no oxygen and having oxygen.

The humic substances in peatlands (depicted, a bog in Scandinavia) work like a gigantic, rechargeable battery.

Photo: Michael Sander, ETH Zurich

Wetlands, including peatlands, have a high content of humic substances, which are organic compounds that form during incomplete decomposition of biomass. Under anoxic conditions, soil bacteria can use these organic compounds during respiration as electron acceptors. Many organisms (including us humans) instead use oxygen as the electron acceptor.

In the mid-1990s, researchers revealed that some anaerobic microorganisms in soils and sediments use humic substances as electron acceptors under anoxic conditions. However, the capacity of these substances to accept electrons is limited. Once the capacity is reached (i.e., the battery is fully charged), the bacteria in anoxic systems utilize other electron acceptors. If carbon dioxide is used as electron acceptor, the potent greenhouse gas methane is formed. Wetlands are responsible for fifteen to forty per cent of the global methane flux into the atmosphere. However, many wetlands release less methane than expected based on their areas and the microbial activity in these systems. This finding suggests that there are natural processes that suppress methane formation.

In a study published in Nature Geoscience, researchers including Dr. Michael Sander, a senior scientist in the Environmental Chemistry Group of ETH-Zurich Professor Kristopher McNeill, have now presented a process that likely contribute to the comparatively small releases of methane.
Humic substances short-circuit electrons to oxygen

With the aid of a model system, the researchers demonstrated that the capacities of humic substances to accept electrons can be fully regenerated if the humic substances charged by the microorganisms are periodically brought in contact with oxygen. The charged humic substances then release the electrons they have accepted under oxygen-free conditions to the newly introduced oxygen. If the system subsequently turns anoxic again, the bacteria may again use the humic substances as electron acceptors, thereby supressing the number of electrons that are transferred to carbon dioxide. Consequently, this process of short-circuiting electrons from anaerobic respiration via humic substances to oxygen may suppress the formation of methane in natural systems that are periodically anoxic and that contain a high content of humic substances.

In their lab model, the researchers used the bacterium Shewanella oneidensis MR-1, which was originally isolated from the sediment of a lake in New York State and which is easily cultivated in the lab. This organism is a facultative anaerobe bacterium, which means that it can live under both anoxic and oxic conditions. The researchers used four different well-characterized humic substances as electron acceptors.
Implications for wetlands

The results of this study contribute to a better understanding of carbon dynamics in temporarily anoxic wetlands. The process described in the study is expected to occur on a large scale, for instance in peatlands. If the water level in a peatland drops, oxygen enters into parts that were previously anoxic. The humic substances in these parts, which were charged by microorganisms in the absence of oxygen, then release the electrons to oxygen and thereby regenerate their capacity to accept electrons. Peatland soils therefore work like gigantic batteries that are periodically charged and discharged. This charging and discharging is expected to suppress the formation of methane in these systems.

The researchers estimated the extent to which this process supresses the formation of methane in northern peatlands. They estimated how many electrons humic substances accept under anoxic conditions and, under subsequent oxic condition, donate to oxygen. This estimation shows that methane emissions from these systems would be up to 170 per cent higher relative to the amount of methane that is currently released. “These results shows that electron transfer to and from humic substances is an important process with global implications,” says Sander. In order to further investigate this process, the researchers will continue with lab studies and, in the coming summer, also conduct field measurements in a peatland in Central Sweden.

A giant sunspot – a magnetically strong and complex region on the sun's surface – has just appeared over the sun's horizon. This is the third trip for this region across the face of the sun, which takes approximately 27 days to make a complete rotation.

A giant sunspot appeared on Feb. 25, 2014, for its third trip across the face of the sun. This blend of two images from NASA's Solar Dynamics Observatory shows the sunspot in visible light and an X-class flare observable in ultraviolet light.

Image Credit: NASA/SDO/Goddard Space Flight Center

Scientists track sunspots that are part of active regions, which often produce large explosions on the sun such as solar flares and coronal mass ejections, or CMEs. Each time an active region appears it is assigned a number. Active regions that have survived their trip around the back of the sun and reappear are assigned a new number – a convention left over from when we had no telescopes observing the far side of the sun and so could not be sure that the new sunspot was indeed the same as the old one. This active region is currently labeled AR11990. Last time around it was labeled AR11967and its first time it was AR11944.

During its three trips thus far, this region has produced two significant solar flares, labeled as the strongest kind of flare, an X-class. It has also produced numerous mid-level and smaller flares. While many sunspots do not last more than a couple of weeks, there have been sunspots known to be stable for many months at a time.

The sun emitted a significant solar flare, peaking at 7:49 p.m. EST on Feb. 24, 2014. NASA's Solar Dynamics Observatory, which keeps a constant watch on the sun, captured images of the event in multiple wavelengths.

Image Credit: SDO/NASA Goddard's Scientific Visualization Studio

This movie shows imagery from NASA's Solar Dynamics Observatory as the sun emitted an X-class flare on Jan. 7, 2014. The movie shows light in the 1600 Angstrom wavelength showing both sunspots visible on the sun's surface and the flare in the solar atmosphere. NOTE: This video loops 4 times.

Image Credit: NASA/SDO/Goddard

Studying what causes active regions to appear and disappear over time, as well as how long they remain stable, is key to understanding the origins of space weather that can impact Earth’s technological infrastructure.

The aurora shimmered in the night sky over Tromsø, Norway, on Jan. 9, 2014, after a coronal mass ejection arrived in near-Earth space, following a two-day journey from the sun.

A team of Australian and American astronomers have been studying nearby galaxy M83 and have found a new superpowered small black hole, named MQ1, the first object of its kind to be studied in this much detail.

Astronomers have found a few compact objects that are as powerful as MQ1, but have not been able to work out the size of the black hole contained within them until now.

Nearby spiral galaxy M83 and the MQ1 system with jets, as seen by the Hubble Space Telescope. The blue circle marks the position of the MQ1 system in the galaxy (shown inset).

The team observed the MQ1 system with multiple telescopes and discovered that it is a standard-sized small black hole, rather than a slightly bigger version that was theorised to account for all its power.

Curtin University senior research fellow Dr Roberto Soria, who is part of the International Centre for Radio Astronomy Research (ICRAR) and led the team investigating MQ1, said it was important to understand how stars were formed, how they evolved and how they died, within a spiral shaped galaxy like M83.

“MQ1 is classed as a microquasar - a black hole surrounded by a bubble of hot gas, which is heated by two jets just outside the black hole, powerfully shooting out energy in opposite directions, acting like cosmic sandblasters pushing out on the surrounding gas,” Dr Soria said.

“The significance of the huge jet power measured for MQ1 goes beyond this particular galaxy: it helps astronomers understand and quantify the strong effect that black hole jets have on the surrounding gas, which gets heated and swept away.

“This must have been a significant factor in the early stages of galaxy evolution, 12 billion years ago, because we have evidence that powerful black holes like MQ1, which are rare today, were much more common at the time.”

“By studying microquasars such as MQ1, we get a glimpse of how the early universe evolved, how fast quasars grew and how much energy black holes provided to their environment.”As a comparison, the most powerful microquasar in our galaxy, known as SS433, is about 10 times less powerful than MQ1.

Although the black hole in MQ1 is only about 100 kilometres wide, the MQ1 structure - as identified by the Hubble Space Telescope - is much bigger than our Solar System, as the jets around it extend about 20 light years from either side of the black hole.

Black holes vary in size and are classed as either stellar mass (less than about 70 times the mass of our Sun) or supermassive (millions of times the mass of our Sun, like the giant black hole that is located in the middle of the Milky Way).

MQ1 is a stellar mass black hole and was likely formed when a star died, collapsing to leave behind a compact mass.

The discovery of MQ1 and its characteristics is just one of the results of the comprehensive study of galaxy M83, a collection of millions of stars located 15 million light years away from Earth.

M83, the iconic Southern-sky galaxy, is being mapped with the Hubble Space and Magellan telescopes (detecting visible light), the Chandra X-ray Observatory (detecting light in X-ray frequencies), the Australia Telescope Compact Array and the Very Large Array (detecting radio waves).

ICRAR is a joint venture between Curtin University and The University of Western Australia which receives funding from the State Government of Western Australia.

Researchers have discovered how Native Americans may have survived the last Ice Age after splitting from their Asian relatives 25,000 years ago. A population of hundreds or thousands likely lived on land bridge for up to 10,000 years

Academics at Royal Holloway, University of London, and the Universities of Colorado and Utah have analysed fossils which revealed that the ancestors of Native Americans may have set up home in a region between Siberia and Alaska which contained woody plants that they could use to make fires. The discovery breaks new ground as until now no-one had any idea of where the native Americans spent the next 10,000 years before they appeared in Alaska and the rest of the North America.

A photo of Alaska's shrub tundra environment today showing birch shrubs in the foreground and spruce trees scattered around Eight Mile Lake, located in the foothills of the Alaska Range.Credit: Nancy Bigelow, University of Alaska Fairbanks

Professor Scott Elias, from the Department of Geography at Royal Holloway said: "This work fills in a 10,000-year missing link in the story of the peopling of the New World. "

The findings, which are published in the journal Science, reveal that the ancestors of Native Americans may have lived on the Bering Land Bridge, which is now under the waters of the Bering and Chukchi Seas. The land bridge and some adjacent regions were not as dry as the rest of Beringia, and this central part of Beringia was covered in shrub tundra - the dominant vegetation in modern Arctic Alaska. It is dominated by dwarf willow and birch shrubs, mosses and lichens.

Professor Elias explained: "We believe that these ancestors survived on the shrub tundra of the Bering Land Bridge because this was the only region of the Arctic where any woody plants were growing. They needed the wood for fuel to make camp fires in this bitterly cold region of the world. They would have used dwarf shrub wood to get a small fire going, then placed large mammal bones on top of the fire, to ignite the fats inside the bones. Once burning, large leg bones of ice-age mammals would have burned for hours, keeping people alive through Arctic winter nights."

The theory, now known as the "Beringia Standstill," was first proposed in 1997 by two Latin American geneticists and refined in 2007 by a team led by the University of Tartu in Estonia that sampled mitrochondrial DNA from more than 600 Native Americans. The researchers found that mutations in the DNA indicated a group of their direct ancestors from Siberia was likely isolated for at least several thousand years in the region of the Bering Land Bridge, the now-submerged plain that lies between northeast Asia and Alaska once exposed by a significantly lower sea level.

CU-Boulder researcher John Hoffecker, lead author of a short paper article appearing in the Feb. 28 issue of Science magazine, said the Beringia Standstill model gained little traction outside of the genetics community after it was proposed and has been seen by some scientists outside of the field as far-fetched. But the new paper by Hoffecker and co-authors Scott Elias of Royal Holloway, University of London, and Dennis O'Rourke of the University of Utah adds credence to the Beringia Standstill idea by further linking the genetics to the paleoecological evidence.

"A number of supporting pieces have fallen in place during the last decade, including new evidence that central Beringia supported a shrub tundra region with some trees during the last glacial maximum and was characterized by surprisingly mild temperatures, given the high latitude," said Hoffecker of CU-Boulder's Institute of Arctic and Alpine Research. The last glacial maximum peaked roughly 21,000 years ago and was marked by the growth of vast ice sheets in North America and Europe.

While a debate rages on about when early humans first migrated into the New World, many archaeologists now believe it was sometime around 15,000 years ago after retreating glaciers opened access to coastal and interior routes into North America.

The relatively mild summer climate in Beringia at the time was caused by North Pacific circulation patterns that brought moist and relatively warm air to the region during the last glacial maximum. Geologists believe the Beringia gateway between Siberia and Alaska was more than 600 miles wide at the time.

This map shows the outlines of modern Siberia (left) and Alaska (right) with dashed lines. The broader area in darker green (now covered by ocean) represents the Bering land bridge near the end of the last glacial maximum, a period that lasted from 28,000 to 18,000 years ago when sea levels were low and ice sheets extended south into what is now the northern part of the lower 48 states. University of Utah anthropologist Dennis O'Rourke argues in the Feb. 28 issue of the journal Science that the ancestors of Native Americans migrated from Asia onto the Bering land bridge or "Beringia" some 25,000 years ago and spent 10,000 years there until they began moving into the Americas 15,000 years ago as the ice sheets melted.Credit: Wlliam Manley, Institute of Arctic and Alpine Research, University of Colorado.

Hoffecker and others are now theorizing that a population of hundreds or thousands of people parked itself in central Beringia for 5,000 years or more. One key to the extended occupation may have been the presence of wood in some places to use as a fuel to supplement bone, which burns hot and fast. Experiments have shown that at least some wood is necessary to make bone practical as a fuel.

Elias, a paleoecologist and also an INSTAAR affiliate, said research using fossil pollen, plant and insect material from sediment cores from the now submerged landscape show that the Bering Land Bridge tundra environment contained enough woody plants and trees like birch, willow and alder to provide a supplement to bone.

Work by Elias and others included the analysis of certain beetle species that live in very specific temperature zones, allowing them to be used as tiny thermometers. The insects indicated that temperatures there were relatively mild during last glacial maximum that ran from about 27,000 years to 20,000 years ago, only slightly cooler than temperatures in the region today.

"The climate on the land bridge and adjacent parts of Siberia and Alaska was a bit wetter than the interior regions like central Alaska and the Yukon, but not a lot warmer," said Elias. "Our data show that woody shrubs were available on the land bridge, which would have facilitated the making of fires by the people there."

Evidence from the 2007 study indicated a set of genetic mutations in mitochondrial DNA, which is passed down from mother to offspring, clearly accumulated after the divergence of people from their Asian parent groups in Siberia but before their dispersal throughout the Western Hemisphere, said O'Rourke. In addition, ancient DNA from human skeletal remains found at a 24,000-year-old archaeological site in southern Siberia also appears consistent with the divergence of Native American groups from their Asian forbearers by that time window, he said.

"The genetic record has been very clear for several years that the Native American genome must have arisen in an isolated population at least by 25,000 years ago, and the bulk of the migrants to the Americas really didn't arrive south of the ice sheets until nearly 15,000 years ago," O'Rourke said. "The paleoecological data, which I think most geneticists have not been familiar with, indicate that Beringia was not a uniform environment, and there was a shrub tundra region, or refugium, that likely provided habitats conducive to continuous human habitation."

"From my view the genetics and paleoecology data come together nicely," said Hoffecker, who co-authored a 2007 book with Elias titled "The Human Ecology of Beringia." While the weakest link to the Out of Beringia theory is the lack of archaeological evidence, Hoffecker believes future research on now submerged parts of Beringia as well as lowlands in western Alaska and eastern Siberia that still remain above water may hold clues to ancient habitation by Beringia residents, who eventually moved on to be the first group to inhabit the Americas.

Hoffecker also believes that the Beringia inhabitants during the last glacial maximum could have made successful hunting forays into the uninhabited steppe-tundra region to both the east and west, where drier conditions and more grass supported a plentiful array of large grazing animals, including steppe bison, horse and mammoth.

There is now solid evidence for humans in Beringia before the last glacial maximum, as geneticists first predicted in 1997, said Hoffecker. After the maximum, there are two sets of archaeological remains dating to less than 15,000 years ago. "One represents a late migration from Asia into Alaska at that time," he said. "The other has no obvious source outside Beringia and may represent the people who are thought to have sheltered on the land bridge during the glacial maximum.

"If we are looking for a place to put all of these people during the last glacial maximum, Beringia may be the only realistic option," said Hoffecker.

The academics made the discovery after analysing insect and plant fossils extracted from sediment cores taken from the ancient land bridge surface, which lies on the sea floor 50-60 metres below the water's surface.

Genetic and environmental evidence indicates that after the ancestors of Native Americans left Asia, they spent 10,000 years in shrubby lowlands on a broad land bridge that once linked Siberia and Alaska. Archaeological evidence is lacking because it drowned beneath the Bering Sea when sea levels rose.

University of Utah anthropologist Dennis O'Rourke and two colleagues make that argument in the Friday, Feb. 28, issue of the journal Science. They seek to reconcile existing genetic and paleoenvironmental evidence for human habitation on the Bering land bridge – also called Beringia – with an absence of archaeological evidence.

University of Utah anthropologist Dennis O'Rourke co-authored a Perspective column in the journal Science arguing that genetic, ancient environmental and archaeological evidence can be reconciled in support of the idea that the ancestors of Native Americans spent some 10,000 years living in brushy refuges on the Bering land bridge en route from Siberia to the Americas. Contrary to common misperception, the "bridge" really was a landmass 1,000 miles wide from north to south and covered most of the area now shown as ocean on the map around, behind and above O'Rourke's head.

Credit: Lee J. Siegel, University of Utah.

O'Rourke says cumulative evidence indicates the ancestors of Native Americans lived on the Bering land bridge "in the neighborhood of 10,000 years," from roughly 25,000 years ago until they began moving into the Americas about 15,000 years ago once glacial ice sheets melted and opened migration routes.

O'Rourke co-authored the Science Perspective column – titled "Out of Beringia?" – with archaeologist John Hoffecker of the University of Colorado at Boulder, and Scott Elias, a paleoecologist at the University of London. Perspective columns in Science don't feature research by the authors, but instead are meant to highlight and provide context for exciting new research in a field or across fields.

"Nobody disputes that the ancestors of Native American peoples came from Asia over the coast and interior of the land bridge" during an ice age called the "last glacial maximum," which lasted from 28,000 to at least 18,000 years ago, O'Rourke says,

The ice sheets extended south into the Pacific Northwest, Wyoming, Wisconsin and Ohio. Large expanses of Siberia and Beringia were cold but lacked glaciers.

The absence of archaeological sites and the inhospitable nature of open, treeless landcape known as tundra steppe mean that "archaeologists have not given much credence to the idea there was a population that lived on the Bering land bridge for thousands of years," he adds.

O'Rourke and colleagues say that in recent years, paleoecologists – scientists who study ancient environments – drilled sediment cores from the Bering Sea and Alaskan bogs. Those sediments contain pollen, plant and insect fossils, suggesting the Bering land bridge wasn't just barren, grassy tundra steppe but was dotted by "refugia" or refuges where there were brushy shrubs and even trees such as spruce, birch, willow and alder.

"We're putting it together with the archaeology and genetics that speak to American origins and saying, look, there was an environment with trees and shrubs that was very different than the open, grassy steppe. It was an area where people could have had resources, lived and persisted through the last glacial maximum in Beringia," O'Rourke says. "That may have been critical for the people to subsist because they would have had wood for construction and for fires. Otherwise, they would have had to use bone, which is difficult to burn."

A Frozen, Isolated Dawn for the Earliest Americans

This map shows the outlines of modern Siberia (left) and Alaska (right) with dashed lines. The broader area in darker green (now covered by ocean) represents the Bering land bridge near the end of the last glacial maximum, a period that lasted from 28,000 to 18,000 years ago when sea levels were low and ice sheets extended south into what is now the northern part of the lower 48 states. University of Utah anthropologist Dennis O'Rourke argues in the Feb. 28 issue of the journal Science that the ancestors of Native Americans migrated from Asia onto the Bering land bridge or "Beringia" some 25,000 years ago and spent 10,000 years there until they began moving into the Americas 15,000 years ago as the ice sheets melted.Credit: Wlliam Manley, Institute of Arctic and Alpine Research, University of Colorado.

During the last glacial maximum, thick glacial ice sheets extended south into what now is the northern United States, sea levels dropped some 400 feet, O'Rourke says. As the glaciers melted, sea levels began to rise, reaching current levels 6,000 years ago.

During the long glacial period, Siberia and Alaska were linked by the Bering land bridge, which contrary to the name's implication, really was a huge swath of land north, between and south of Siberia and Alaska, at the present sites of the Chukchi Sea, the Bering Strait and the Bering Sea, respectively.

At its largest extent, Beringia measured as much as 1,000 miles from north to south and as much as 3,000 miles from Siberia's Verkoyansk Range east to the Mackenzie River in in Canada.

The theory that humans inhabited the Bering land bridge for some 10,000 years "helps explain how a Native American genome (genetic blueprint) became separate from its Asian ancestor," O'Rourke says.

"At some point, the genetic blueprint that defines Native American populations had to become distinct from that Asian ancestry," he explains. "The only way to do that was for the population to be isolated. Most of us don't believe that isolation took place in Siberia because we don't see a place where a population could be sufficiently isolated. It would always have been in contact with other Asian groups on its periphery."

"But if there were these shrub-tundra refugia in central Beringia, that provided a place where isolation could occur" due to distance from Siberia, O'Rourke says.

Genetic and Paleoenvironmental Evidence

O'Rourke and colleagues point to a study of mitochondrial DNA – genetic information passed by mothers – sampled from Native Americans throughout the Americas. The study found that the unique genome or genetic blueprint of Native Americans arose sometime before 25,000 years ago but didn't spread through the Americas until about 15,000 years ago.

"This result indicated that a substantial population existed somewhere, in isolation from the rest of Asia, while its genome differentiated from the parental Asian genome," O'Rourke says. "The researchers suggested Beringia as the location for this isolated population, and suggested it existed there for several thousand years before members of the population migrated southward into the rest of North and, ultimately, South America as retreating glaciers provided routes for southern migration."

"Several other genetic-genomic analyses of Native American populations have resulted in similar conclusions," he adds.

"For a long time, many of us thought the land bridge was a uniform tundra-steppe environment" – a broad windswept grassland devoid of shrubs and trees, O'Rourke says. But in recent years, sediment cores drilled in the Bering Sea and along the Alaskan coast – the now-submerged lowlands of Beringia – found pollens of trees and shrubs.

That "suggests Beringia was not a uniform tundra-steppe environment, but a patchwork of environments, including substantial areas of lowland shrub tundra," O'Rourke says. "These shrub-tundra areas were likely refugia for a population that would be invisible archaeologically, since the former Beringian lowlands are now submerged."

"Large herd animals like bison or mammoths likely lived on the highland steppe tundra because they graze. Many smaller animals, birds, elk and moose (which browse shrubs instead of grazing on grass) would have been in the shrub tundra," he adds.

Other research indicates "that much of Beringia – particularly the lowlands – appears to have had average summer temperatures nearly identical (or only slightly cooler in some regions) to those in the region today," O'Rourke says. "The local environments likely were not as daunting as many have assumed for years. They probably hunkered down pretty good in the winter though. It would have been cold."

The idea that rising sea levels covered evidence of human migration to the Americas has long been cited by researchers studying how early Native Americans moved south along the Pacific coast as the glaciers receded and sea levels rose. O'Rourke says the idea hasn't been used before to explain the scarcity of archaeological sites in Alaska and Siberia, which were highlands when the land bridge was exposed.

But O'Rourke and his colleagues say archaeological sites must be found in Beringia if the long human layover there is to be confirmed. Although most such sites are underwater, some evidence of human habitation in shrub tundra might remain above sea level in low-lying portions of Alaska and eastern Chukotka (in Russia)."

Thursday, February 27, 2014

MIT group shows xylem tissue in sapwood can filter bacteria from contaminated water.

If you’ve run out of drinking water during a lakeside camping trip, there’s a simple solution: Break off a branch from the nearest pine tree, peel away the bark, and slowly pour lake water through the stick. The improvised filter should trap any bacteria, producing fresh, uncontaminated water.

In fact, an MIT team has discovered that this low-tech filtration system can produce up to four liters of drinking water a day — enough to quench the thirst of a typical person.

In a paper published this week in the journal PLoS ONE, the researchers demonstrate that a small piece of sapwood can filter out more than 99 percent of the bacteria E. coli from water. They say the size of the pores in sapwood — which contains xylem tissue evolved to transport sap up the length of a tree — also allows water through while blocking most types of bacteria.

Co-author Rohit Karnik, an associate professor of mechanical engineering at MIT, says sapwood is a promising, low-cost, and efficient material for water filtration, particularly for rural communities where more advanced filtration systems are not readily accessible.

Researchers design a simple filter by peeling the bark off a small section of white pine, then inserting and securing it within plastic tubing.

Image courtesy of the researchers

“Today’s filtration membranes have nanoscale pores that are not something you can manufacture in a garage very easily,” Karnik says. “The idea here is that we don’t need to fabricate a membrane, because it’s easily available. You can just take a piece of wood and make a filter out of it.”

The paper’s co-authors include Michael Boutilier and Jongho Lee from MIT, Valerie Chambers from Fletcher-Maynard Academy in Cambridge, Mass., and Varsha Venkatesh from Jericho High School in Jericho, N.Y.

Tapping the flow of sap

There are a number of water-purification technologies on the market today, although many come with drawbacks: Systems that rely on chlorine treatment work well at large scales, but are expensive. Boiling water to remove contaminants requires a great deal of fuel to heat the water. Membrane-based filters, while able to remove microbes, are expensive, require a pump, and can become easily clogged.

Sapwood may offer a low-cost, small-scale alternative. The wood is comprised of xylem, porous tissue that conducts sap from a tree’s roots to its crown through a system of vessels and pores. Each vessel wall is pockmarked with tiny pores called pit membranes, through which sap can essentially hopscotch, flowing from one vessel to another as it feeds structures along a tree’s length. The pores also limit cavitation, a process by which air bubbles can grow and spread in xylem, eventually killing a tree. The xylem’s tiny pores can trap bubbles, preventing them from spreading in the wood.

“Plants have had to figure out how to filter out bubbles but allow easy flow of sap,” Karnik observes. “It’s the same problem with water filtration where we want to filter out microbes but maintain a high flow rate. So it’s a nice coincidence that the problems are similar.”

Seeing red

To study sapwood’s water-filtering potential, the researchers collected branches of white pine and stripped off the outer bark. They cut small sections of sapwood measuring about an inch long and half an inch wide, and mounted each in plastic tubing, sealed with epoxy and secured with clamps.

Before experimenting with contaminated water, the group used water mixed with red ink particles ranging from 70 to 500 nanometers in size. After all the liquid passed through, the researchers sliced the sapwood in half lengthwise, and observed that much of the red dye was contained within the very top layers of the wood, while the filtrate, or filtered water, was clear. This experiment showed that sapwood is naturally able to filter out particles bigger than about 70 nanometers.

However, in another experiment, the team found that sapwood was unable to separate out 20-nanometer particles from water, suggesting that there is a limit to the size of particles coniferous sapwood can filter.

Picking the right plant

Finally, the team flowed inactivated, E. coli-contaminated water through the wood filter. When they examined the xylem under a fluorescent microscope, they saw that bacteria had accumulated around pit membranes in the first few millimeters of the wood. Counting the bacterial cells in the filtered water, the researchers found that the sapwood was able to filter out more than 99 percent of E. coli from water.

Karnik says sapwood likely can filter most types of bacteria, the smallest of which measure about 200 nanometers. However, the filter probably cannot trap most viruses, which are much smaller in size.

Karnik says his group now plans to evaluate the filtering potential of other types of sapwood. In general, flowering trees have smaller pores than coniferous trees, suggesting that they may be able to filter out even smaller particles. However, vessels in flowering trees tend to be much longer, which may be less practical for designing a compact water filter.

Designers interested in using sapwood as a filtering material will also have to find ways to keep the wood damp, or to dry it while retaining the xylem function. In other experiments with dried sapwood, Karnik found that water either did not flow through well, or flowed through cracks, but did not filter out contaminants.

“There’s huge variation between plants,” Karnik says. “There could be much better plants out there that are suitable for this process. Ideally, a filter would be a thin slice of wood you could use for a few days, then throw it away and replace at almost no cost. It’s orders of magnitude cheaper than the high-end membranes on the market today.”

While the pores in sapwood are too big to filter out salts, Saurya Prakash, an assistant professor of mechanical engineering at Ohio State University, says the design could be useful in parts of the world where people collect surface water, which can be polluted with fine dust and particles of decaying plant and animal matter. Most of this detritus, Prakash says, could easily be filtered out by the group’s design.

“The xylem tissue acts as a natural filter, similar to a manmade membrane,” says Prakash, who was not involved in the research. “The study by the Karnik group shows that use of abundant, naturally occurring materials could pave the way for a new generation of water filters that are potentially low-cost enough to be disposable.”

This research was supported by the James H. Ferry Jr. Fund for Innovation in Research Education.

Mute the song playing on your smartphone in your pocket by flicking your index finger in the air, or pause your “This American Life” podcast with a small wave of the hand. This kind of gesture control for electronics could soon become an alternative to touchscreens and sensing technologies that consume a lot of power and only work when users can see their smartphones and tablets.

Credit: U of Washington

The AllSee prototype is integrated with an off-the-shelf mobile phone. This technology enables new applications such as gesture recognition with the phone still in your pocket.

University of Washington computer scientists have built a low-cost gesture recognition system that runs without batteries and lets users control their electronic devices hidden from sight with simple hand movements. The prototype, called “AllSee,” uses existing TV signals as both a power source and the means for detecting a user’s gesture command.

“This is the first gesture recognition system that can be implemented for less than a dollar and doesn’t require a battery,” said Shyam Gollakota, a UW assistant professor of computer science and engineering. “You can leverage TV signals both as a source of power and as a source of gesture recognition.”

The researchers built a small sensor that can be placed on an electronic device such as a smartphone. The sensor uses an ultra-low-power receiver to extract and classify gesture information from wireless transmissions around us. When a person gestures with the hand, it changes the amplitude of the wireless signals in the air. The AllSee sensors then recognize unique amplitude changes created by specific gestures.

Credit: U of Washington

AllSee detects the unique signal changes (shown on the oscilloscope) and classifies a rich set of hand gestures.

Sensors use three to four times less power than existing gesture recognition systems by harvesting power from wireless transmissions. This allows for mobile devices to always have the gesture technology on and enabled.

Gesture recognition already is possible on some mobile devices, including the Samsung Galaxy S4 smartphone. But users have to first manually enable the feature and be able to see the device for the gesture technology to work, and if left on, the gesture system quickly drains the phone’s battery. In contrast, AllSee consumes only tens of microwatts of power and can always be left on. The user could gesture at the phone in a pocket or handbag to change the volume or mute the phone without having to touch or see the phone.

Credit: U of Washington

Beyond mobile devices, AllSee can also enable interaction with Internet of Things devices such as home monitoring solutions.

This technology could allow sensors to be attached to household electronics, making it possible to interact with everyday objects using gestures and also connect them to the Internet and to each other in an “Internet of Things” world.

“Beyond mobile devices, AllSee can enable interaction with Internet of Things devices. These sensing devices are increasingly smaller electronics that can’t operate with usual keypads, so gesture-based systems are ideal,” said Bryce Kellogg, a UW doctoral student in electrical engineering.

The UW team tested AllSee’s capabilities on smartphones and battery-free sensors using eight different hand gestures such as pushing or pulling to zoom in and out. The prototype could correctly identify the gestures more than 90 percent of the time while performed more than 2 feet away from the device.

Researchers have tested the technology for response time and whether it can distinguish between other motions and those directed at it. They found that the technology’s response time is less than 80 microseconds, which is 1,000 times faster than blinking an eye.

“This enables a seamless and interactive experience for the user,” said Vamsi Talla, a UW doctoral student in electrical engineering. The researchers also designed a wake-up gesture that allows the system not to confuse unintentional motions for actual gestures.

This technology builds on previous work by Gollakota on leveraging Wi-Fi signals around us for gesture recognition around the home. Prior wireless gesture recognition techniques, however, consume tens of watts of power and aren’t suitable for mobile or Internet of Things devices.

The research is funded by a Google Faculty Research Award and the Washington Research Foundation.

Researchers say Ross Sea will reverse current trend, be largely ice free in summer by 2100

Antarctica’s Ross Sea is one of the few polar regions where summer sea-ice coverage has increased during the last few decades, bucking a global trend of drastic declines in summer sea ice across the Arctic Ocean and in two adjacent embayments of the Southern Ocean around Antarctica.

Emperor Penguins: Changes in the extent and duration of Ross Sea ice will significantly impact marine life in what is one of the world’s most productive and unspoiled marine ecosystems, where rich blooms of phytoplankton feed krill, fish, and higher predators such as penguins.Photo courtesy of Walker Smith.

Now, a modeling study led by Professor Walker Smith of the Virginia Institute of Marine Science suggests that the Ross Sea’s recent observed increase in summer sea-ice cover is likely short-lived, with the area projected to lose more than half its summer sea ice by 2050 and more than three quarters by 2100.

These changes, says Smith, will significantly impact marine life in what is one of the world’s most productive and unspoiled marine ecosystems, where rich blooms of phytoplankton feed krill, fish, and higher predators such as whales, penguins, and seals.

Smith says “The Ross Sea is critically important in regulating the production of Antarctica’s sea ice overall and is biologically very productive, which makes changes in its physical environment of global concern. Our study predicts that it will soon reverse its present trend and experience major drops in ice cover in summer, which, along with decreased mixing of the vertical column, will extend the season of phytoplankton growth. These changes will substantially alter the area’s pristine food web.”

Researchers attribute the observed increase in summertime sea ice in the Ross Sea—where the number of days with ice cover has grown by more two months over the past three decades—to a complex interplay of factors, including changes in wind speed, precipitation, salinity, ocean currents, and air and water temperature.

Sea ice covers a large part of the Ross Sea in this summer 2007 photo. A large opening in the ice cover, or polynya, extends to the east.

Photo courtesy of NASA.

But global climate models agree that air temperatures in Antarctica will increase substantially in the coming decades, with corresponding changes in the speed and direction of winds and ocean currents. When Smith and his colleagues fed these global projections into a high-resolution computer model of air-sea-ice dynamics in the Ross Sea, they saw a drastic reduction in the extent and duration of summer sea ice.

The modeled summer sea ice concentrations decreased by 56% by 2050 and 78% by 2100. The ice-free season also grew much longer, with the mean day of retreat in 2100 occurring 11 days earlier and the advance occurring 16 days later than now.

Also changed was the duration and depth of the “shallow mixed layer,” the zone where most phytoplankton live. “Our model projects that the shallow mixed layer will persist for about a week longer in 2050, and almost three weeks longer in 2100 than now,” says Smith. “The depth of the shallow mixed layer will also decrease significantly, with its bottom 12% shallower in 2050, and 44% shallower in 2100 than now.”

The extent and duration of ice cover in the Ross Sea depends on a complex interplay of factors, including changes in wind speed, precipitation, salinity, ocean currents, and air and water temperature.

Credit: Virginia Institute of Marine Science

For Smith, these changes in ice, atmosphere, and ocean dynamics portend major changes in the Antarctic food web. On the bright side, the decrease in ice cover will bring more light to surface waters, while a more persistent and shallower mixed layer will concentrate phytoplankton and nutrients in this sunlit zone. These changes will combine to encourage phytoplankton growth, particularly for single-celled organisms called diatoms, with ripples of added energy potentially moving up the food web.

But, Smith warns, the drop in ice cover will negatively affect several other important species that are ice-dependent, including crystal krill and Antarctic silverfish. A decrease in krill would be particularly troublesome, as these are the major food source for the Ross Sea’s top predators—minke whales, Adélie and Emperor penguins, and crabeater seals.

Overall, says Smith, “our results suggest that phytoplankton production will increase and become more diatomaceous. Other components of the Ross Sea food web will likely be severely disrupted, creating significant but unpredictable impacts on the ocean’s most pristine ecosystem.”

Endocrine disrupters are not the only worrying chemicals that ordinary consumers are exposed to in everyday life. Also nanoparticles of silver, found in e.g. dietary supplements, cosmetics and food packaging, now worry scientists. A new study from the University of Southern Denmark shows that nano-silver can penetrate our cells and cause damage.

Thiago Verano-Braga, Ph.D., of the University of Southern Denmark.

Credit: Birgitte Svennevig/University of Southern Denmark

Silver has an antibacterial effect and therefore the food and cosmetic industry often coat their products with silver nanoparticles. Nano-silver can be found in e.g. drinking bottles, cosmetics, band aids, toothbrushes, running socks, refrigerators, washing machines and food packagings.

"Silver as a metal does not pose any danger, but when you break it down to nano-sizes, the particles become small enough to penetrate a cell wall. If nano-silver enters a human cell, it can cause changes in the cell", explain Associate Professor Frank Kjeldsen and PhD Thiago Verano-Braga, Department of Biochemistry and Molecular Biology at the University of Southern Denmark.

Together with their research colleagues they have just published the results of a study of such cell damages in the journal ACS Nano.

The researchers examined human intestinal cells, as they consider these to be most likely to come into contact with nano-silver, ingested with food.

"We can confirm that nano-silver leads to the formation of harmful, so called free radicals in cells. We can also see that there are changes in the form and amount of proteins. This worries us", say Frank Kjeldsen and Thiago Verano-Braga.

Associate professor Frank Kjeldsen of the University of Southern Denmark.

Credit: University of Southern Denmark

A large number of serious diseases are characterized by the fact that there is an overproduction of free radicals in cells. This applies to cancer and neurological diseases such as Alzheimer's and Parkinson's.

Kjeldsen and Verano-Braga emphasizes that their research is conducted on human cells in a laboratory, not based on living people. They also point out that they do not know how large a dose of nano-silver, a person must be exposed to for the emergence of cellular changes.

"We don't know how much is needed, so we cannot conclude that nano-silver can make you sick. But we can say that we must be very cautious and worried when we see an overproduction of free radicals in human cells", they say.

Nano-silver is also sold as a dietary supplement, promising to have an antibacterial, anti-flu and cancer-inhibatory effect. The nano-silver should also help against low blood counts and bad skin. In the EU, the marketing of dietary supplements and foods with claims to have medical effects is not allowed. But the nano-silver is easy to find and buy online.

In the wake of the Uiversity of Southern Denmark-research, the Danish Veterinary and Food Administration now warns against taking dietary supplements with nano-silver.

"The recent research strongly suggests that it can be dangerous", says Søren Langkilde from the Danish Veterinary and Food Administration to the Danish Broadcasting Corporation (DR).###

A study of the jaws of one of the earliest known limbed vertebrates shows the species still fed underwater, not on land.

Scientists from the University of Lincoln, University of Zurich, University of Cambridge and University of Bristol, developed an innovative new method to infer the feeding mechanism ofAcanthostega – one of the earliest and most primitive tetrapods, the four-legged limbed vertebrates which evolved from fish and include today’s amphibians, reptiles, birds and mammals.

Acanthostega was one of the earliest and most primitive tetrapods

Credit: University Museum of Zoology, Cambridge

Acanthostega is regarded as one of the best known early tetrapods and has played a key role in debates about tetrapod origins since spectacular new specimens were discovered in Greenland in 1987. Dating back to some 360 million years ago (end of the Devonian period), it has often been seen as a near-perfect fish-tetrapod intermediate.

The UK and Swiss researchers employed advanced statistical methods from a range of disciplines to explore the anatomical, functional and ecological changes associated with the emergence of tetrapods.

They examined the movement and structure of the lower jaws of Acanthostega and several other early tetrapods and tetrapod-like fish. Their observations suggest the Acanthostega jaw was more geared towards feeding under water, indicating that this tetrapod retained a primarily aquatic lifestyle.

Dr Marcello Ruta from the University of Lincoln’s School of Life Sciences said: “The origin of tetrapod from fish is an iconic example of a major evolutionary transition. The fossils ofAcanthostega continue to play an unsurpassed role in our understanding of the fish-tetrapod transition.

“Acanthostega retained many primitive and fish-like features while also displaying unquestionable tetrapod features such as fingers and toes. Its broad snout appears to be consistent with aquatic feeding habits (suction feeding) but its complex cranial joints appear to be similar to those of terrestrial vertebrates and would suggest direct biting on land environments as a means of prey capture. This paradox prompted our study.”

The team examined patterns of jaw shape variation to assess whether the Acanthostega jaw is overall more similar to the jaws of fish or those of tetrapods. They then used advanced engineering methods to simulate biting action.

Dr Ruta said: “The lower jaw of Acanthostega can be shown to be anatomically and functionally similar to the jaws of some early fish and contemporary fish-tetrapod intermediates."

Dr Emily Rayfield from the University of Bristol’s School of Earth Sciences said:“This provides support for the idea that although these animals were amongst the first to evolve limbs with digits, they were still feeding in water rather than moving on to land to catch their prey.”

University of Bristol researchers study genomic data of cyanobacteria to shed new light on how complex life evolved on Earth

It has long been believed that the appearance of complex multicellular life towards the end of the Precambrian (the geologic interval lasting up until 541 million years ago) was facilitated by an increase in oxygen, as revealed in the geological record. However, it has remained a mystery as to why oxygen increased at this particular time and what its relationship was to 'Snowball Earth' – the most extreme climatic changes the Earth has ever experienced – which were also taking place around then.

A plankton bloom in the Capricorn Channel off the Queensland coast of Australia - Trichodesmium — a photosynthetic cyanobacteria and nitrogen fixer.

This new study shows that it could in fact be what was happening to nitrogen at this time that helps solve the mystery.

The researchers, led by Dr Patricia Sanchez-Baracaldo of the University of Bristol, used genomic data to reconstruct the relationships between those cyanobacteria whose photosynthesis in the open ocean provided oxygen in quantities sufficient to be fundamental in the development of complex life on Earth.

Some of these cyanobacteria were also able to transform atmospheric nitrogen into bioavailable nitrogen in sufficient quantities to contribute to the marine nitrogen cycle, delivering 'nitrogen fertiliser' to the ecosystem.

Using molecular techniques, the team were able to date when these species first appeared in the geological record to around 800 million years ago.

Dr Sanchez-Baracaldo, a Royal Society Dorothy Hodgkin Research Fellow in Bristol's Schools of Biological and Geographical Sciences said: "We have known that oxygenic photosynthesis – the process by which microbes fix carbon dioxide into carbohydrates, splitting water and releasing oxygen as a by-product – first evolved in freshwater habitats more than 2.3 billion years ago. But it wasn't until around 800 million years ago that these oxygenating cyanobacteria were able to colonise the vast oceans (two thirds of our planet) and be fertilised by enough bioavailable nitrogen to then produce oxygen – and carbohydrate food – at levels high enough to facilitate the next 'great leap forward' towards complex life.

"Our study suggests that it may have been the fixing of this nitrogen 'fertiliser' in the oceans at this time that played a pivotal role in this key moment in the evolution of life on Earth."

Co-author, Professor Andy Ridgwell said: "The timing of the spread in nitrogen fixers in the open ocean occurs just prior to global glaciations and the appearance of animals. Although further work is required, these evolutionary changes may well have been related to, and perhaps provided a trigger for, the occurrence of extreme glaciation around this time as carbon was now being buried in the sediments on a much larger scale."

Dr Sanchez-Baracaldo added: "It's very exciting to have been able to use state of the art genetic techniques to help solve an age-old mystery concerning one of the most important and pivotal moments in the evolution of life on Earth. In recent years, genomic data has been helping re-tell the story of the origins of life with increasing clarity and accuracy. It is a privilege to be contributing to our understanding of how microorganisms have contributed to make our planet habitable."

New research in the FASEB Journal suggests that consumption of dark chocolate lowers the augmentation index, a key vascular health predictor, and reduces adhesion of white blood cells to the vessel wall.

It might seem too good to be true, but dark chocolate is good for you and scientists now know why. Dark chocolate helps restore flexibility to arteries while also preventing white blood cells from sticking to the walls of blood vessels. Both arterial stiffness and white blood cell adhesion are known factors that play a significant role in atherosclerosis. What's more, the scientists also found that increasing the flavanol content of dark chocolate did not change this effect. This discovery was published in the March 2014 issue of The FASEB Journal.

Dark Chocolate

Credit: Wikipedia

"We provide a more complete picture of the impact of chocolate consumption in vascular health and show that increasing flavanol content has no added beneficial effect on vascular health," said Diederik Esser, Ph.D., a researcher involved in the work from the Top Institute Food and Nutrition and Wageningen University, Division of Human Nutrition in Wageningen, The Netherlands. "However, this increased flavanol content clearly affected taste and thereby the motivation to eat these chocolates. So the dark side of chocolate is a healthy one."

To make this discovery, Esser and colleagues analyzed 44 middle-aged overweight men over two periods of four weeks as they consumed 70 grams of chocolate per day. Study participants received either specially produced dark chocolate with high flavanol content or chocolate that was regularly produced. Both chocolates had a similar cocoa mass content. Before and after both intervention periods, researchers performed a variety of measurements that are important indicators of vascular health. During the study, participants were advised to refrain from certain energy dense food products to prevent weight gain. Scientists also evaluated the sensory properties of the high flavanol chocolate and the regular chocolate and collected the motivation scores of the participants to eat these chocolates during the intervention.

"The effect that dark chocolate has on our bodies is encouraging not only because it allows us to indulge with less guilt, but also because it could lead the way to therapies that do the same thing as dark chocolate but with better and more consistent results," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "Until the 'dark chocolate drug' is developed, however, we'll just have to make do with what nature has given us!"

Loads of studies over the years have shown that children who were breastfed score higher on IQ tests and perform better in school, but the reason why remained unclear. Researchers found responsiveness to children's emotional cues boosts kids' math and reading skills.

Is it the mother-baby bonding time, something in the milk itself or some unseen attribute of mothers who breastfeed their babies?

Now a new study by sociologists at Brigham Young University pinpoints two parenting skills as the real source of this cognitive boost: Responding to children’s emotional cues and reading to children starting at 9 months of age. Breastfeeding mothers tend to do both of those things, said lead study author Ben Gibbs.

Reading to children as early as 9 months of age also significantly improves school readiness

Credit: BYU

“It’s really the parenting that makes the difference,” said Gibbs. “Breastfeeding matters in others ways, but this actually gives us a better mechanism and can shape our confidence about interventions that promote school readiness.”

Gibbs authored the study with fellow BYU professor Renata Forste for the March issue of The Journal of Pediatrics. According to their analysis, improvements in sensitivity to emotional cues and time reading to children could yield 2-3 months’ worth of brain development by age 4 (as measured by math and reading readiness assessments).

“Because these are four-year-olds, a month or two represents a non-trivial chunk of time," Gibbs said. “And if a child is on the edge of needing special education, even a small boost across some eligibility line could shape a child’s educational trajectory.”

The BYU scholars utilized a national data set that followed 7,500 mothers and their children from birth to five years of age. The data set is rich with information on the home environment, including how early and how often parents read to their kids. Additionally, each of the mothers in the study also participated in video-taped activities with their children. As the child tried to complete a challenging task, the mother’s supportiveness and sensitivity to their child’s emotional cues were measured.

The two parenting skills can give kids an extra 2-3 months' worth of brain development

Credit: BYU

The study gained editorial praise from child development expert Sandra Jacobson of Wayne State University School of Medicine. She noted that children in the study who were breastfed for 6 months or longer performed the best on reading assessments because they also “experienced the most optimal parenting practices.

“Gibbs and Forste found that reading to an infant every day as early as age 9 months and sensitivity to the child's cues during social interactions, rather than breastfeeding per se, were significant predictors of reading readiness at age 4 years,” wrote Jacobson.

The BYU researchers note that the most at-risk children are also the least likely to receive the optimal parenting in early childhood. Single moms in the labor force, for example, don’t have the same luxuries when it comes to breastfeeding and quality time with the children. Parents with less education don’t necessarily hear about research-based parenting practices, either.

“This is the luxury of the advantaged,” Forste said. “It makes it harder to think about how we promote environments for disadvantaged homes. These things can be learned and they really matter. And being sensitive to kids and reading to kids doesn’t have to be done just by the mother.”

A bright supernova discovered only six weeks ago in a nearby galaxy is provoking new questions about the exploding stars that scientists use as their main yardstick for measuring the universe.

Called SN 2014J, the glowing supernova was discovered by a professor and his students in the United Kingdom on Jan. 21, about a week after the stellar explosion first became visible as a pinprick of light in its galaxy, M82, 11.4 million light years away. Still visible today through small telescopes in the Big Dipper, it is the brightest supernova seen from Earth since SN1987A, 27 years ago, and may be the closest Type Ia supernova – the kind used to measure cosmic distances – in more than 77 years.

This image features a color composite of SN 2014J in the 'cigar galaxy' M82, 11.4 million light years away, made from KAIT images obtained through several different filters. The supernova is marked with an arrow. Other round objects are relatively nearby stars in our own Milky Way Galaxy.Credit: W. Zheng and A. Filippenko, University of California BerkeleyWhen University of California, Berkeley, astronomer Alex Filippenko's research team looked for the supernova in data collected by the Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory near San Jose, Calif., they discovered that the robotic telescope had actually taken a photo of it 37 hours after it appeared, unnoticed, on Jan. 14.

Combining this observation with another chance observation by a Japanese amateur astronomer, Filippenko's team was able to calculate that SN 2014J had unusual characteristics – it brightened faster than expected for a Type Ia supernova and, even more intriguing, it exhibited the same unexpected, rapid brightening as another supernova that KAIT discovered and imaged last year – SN 2013dy.

"Now, two of the three most recent and best-observed Type Ia supernovae are weird, giving us new clues to how stars explode," said Filippenko, referring to a third, though apparently 'normal,' Type Ia supernova, SN 2011fe, discovered three years ago. "This may be teaching us something general about Type Ia supernovae that theorists need to understand. Maybe what we think of as 'normal' behavior for these supernovae is actually unusual, and this weird behavior is the new normal."

A paper describing the SN 2014J observations – the first published on this newly discovered supernova – was posted online this week by The Astrophysical Journal Letters and will appear in the March 1 print issue.

Type Ia supernovae as standard candles

Astronomers noticed decades ago that Type Ia supernovae explode with about the same brightness, no matter where they are in the universe. This makes them good "standard candles" with which to judge distance. In the 1990s, two teams (both of them included Filippenko) used Type Ia supernovae to determine the distances to galaxies, compared distance with velocity and discovered that the universe is expanding faster and faster, rather than slowing down as expected. The teams' leaders, including UC Berkeley astrophysicist Saul Perlmutter, shared the 2011 Nobel Prize in Physics for this discovery.

While the latest discoveries do not contradict these results, refinements in understanding Type Ia explosions could help improve distance measurements and lead to more precise calculations of the expansion rate of the universe, thereby setting constraints on the nature of "dark energy," a still mysterious energy comprising 70 percent of the universe and thought to be responsible for its acceleration.

The new data also provide information about the physics occurring in the core of the explosion.

A Type Ia supernova is thought to be the explosion of a white dwarf – an old and very dense star that has shrunk from the size of the Sun to the size of Earth. When a white dwarf has a stellar companion, it can sometimes gain matter from it until the white dwarf becomes unstable, completely obliterating itself through a gigantic nuclear explosion.

New telescopes to catch more supernovae

Because of the importance of supernovae in measuring the universe, many new telescopes, such as the Palomar Transient Factor in San Diego County and the Pan-STARRS in Hawaii, continually rescan the sky to discover more of them. The KAIT telescope has a smaller field of view than newer ones do, so Filippenko's team has switched its focus to discovering supernovae earlier: it scans the same patches of sky every night or every other night. The sooner a new explosion is discovered, the sooner astronomers can capture information, such as spectra showing how the supernova brightens in different colors or wavelengths.

Last year, for example, KAIT and Filippenko's Lick Observatory Supernova Search (LOSS) team discovered and photographed SN 2013dy within two and a half hours of its appearance, earlier than for any other Type Ia. KAIT, which is operated by postdoctoral scholar WeiKang Zheng, is programmed to automatically take images of likely supernovae in five different wavelength bands, and in 2012 captured one supernova, SN 2012cg, three minutes after its discovery.

"Very, very early observations give us the most stringent constraints on what the star's behavior really is in the first stages of the explosion, rather than just relying on theoretical speculation or extrapolating back from observations at later times, which is like observing adolescents to understand early childhood," Filippenko said.

The research was funded by the TABASGO Foundation, the Sylvia & Jim Katzman Foundation, the Christopher R. Redlich Fund, Gary and Cynthia Bengier, the Richard and Rhoda Goldman Fund, Weldon and Ruth Wood, and the National Science Foundation.

South Africa has been financing domestic rainwater harvesting tanks in informal low-income settlements and rural areas in five of that nation's nine provinces. But pathogens inhabit such harvested rainwater, potentially posing a public health hazard, especially for children and immunocompromised individuals, according to a team from the University of Stellenbosch. The research was published ahead of print in Applied and Environmental Microbiology.

Pseudomonas

Credit: Wikipedia

International studies had indicated that harvested rainwater frequently harbors pathogens, and that, in light of the financing of harvesting tanks, drove the investigators to study the matter locally, says principal investigator Wesaal Khan.

The sampling was conducted in the Kleinmond Housing Scheme, which was initiated by the South African Council for Scientific and Industrial Research and the Department of Science and Technology. The houses, designed to be sustainable, are approximately 400 square feet, with alternative technologies such as solar panels and the rainwater tanks.

The list of predatory prokaryotes the investigators found includes Legionella (found in 73% of samples), Klebsiella (47%) Pseudomonas (19% of samples), Yersinia (28%), Shigella (27%), and others. They also found some protozoan parasites, including Giardia (25% of samples).

Legionella

Credit: Wikipedia

Many of the pathogens are normal fresh water inhabitants, but Salmonella (6% of samples) indicates human fecal contamination, while Yersinia are markers of fecal contamination by wild and domestic animals, according to the report.

Residents, many of whom are little-educated and unemployed, typically use the rainwater for washing clothes and house-cleaning, but about one quarter of people polled in the study said they used it for drinking, as well. The finding that coliforms and Escherichia coli counts from rainwater samples—markers of fecal contamination—always significantly exceeded drinking water guidelines, reinforces the World Health Organization's opinion that rainwater must be pretreated prior to use for drinking, says Khan.

Rainwater harvesting is needed in South Africa's "informal communities" because residents often depend on communal "standpipe" systems that frequently serve more than 100 people, who may have to walk as far as a third of a mile to get water, says Khan. Approximately 23,000 rainwater tanks have been installed, two thirds of them in the Eastern Cape and one third in KwaZulu Natal. Nearly 20% of South Africans lack sustainable access to water.

A copy of the manuscript can be found online at http://bit.ly/asmtip0214f. The final version of the article is scheduled for the April 2014 issue of Applied and Environmental Microbiology.

Wednesday, February 26, 2014

NASA's Kepler mission announced Wednesday the discovery of 715 new planets. These newly-verified worlds orbit 305 stars, revealing multiple-planet systems much like our own solar system.

The artist concept depicts multiple-transiting planet systems, which are stars with more than one planet. The planets eclipse or transit their host star from the vantage point of the observer. This angle is called edge-on.

Image Credit: NASA

Nearly 95 percent of these planets are smaller than Neptune, which is almost four times the size of Earth. This discovery marks a significant increase in the number of known small-sized planets more akin to Earth than previously identified exoplanets, which are planets outside our solar system.

The histogram shows the number of planets by size for all known exoplanets. The blue bars on the histogram represents all the exoplanets known, by size, before the Kepler Planet Bonanza announcement on Feb. 26, 2014. The gold bars on the histogram represent Kepler's newly-verified planets.

Credit: NASA Ames/W Stenzel

"The Kepler team continues to amaze and excite us with their planet hunting results," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "That these new planets and solar systems look somewhat like our own, portends a great future when we have the James Webb Space Telescope in space to characterize the new worlds.”

Since the discovery of the first planets outside our solar system roughly two decades ago, verification has been a laborious planet-by-planet process. Now, scientists have a statistical technique that can be applied to many planets at once when they are found in systems that harbor more than one planet around the same star.

To verify this bounty of planets, a research team co-led by Jack Lissauer, planetary scientist at NASA's Ames Research Center in Moffett Field, Calif., analyzed stars with more than one potential planet, all of which were detected in the first two years of Kepler's observations -- May 2009 to March 2011.

The research team used a technique called verification by multiplicity, which relies in part on the logic of probability. Kepler observes 150,000 stars, and has found a few thousand of those to have planet candidates. If the candidates were randomly distributed among Kepler's stars, only a handful would have more than one planet candidate. However, Kepler observed hundreds of stars that have multiple planet candidates. Through a careful study of this sample, these 715 new planets were verified.

The histogram shows the number of planet discoveries by year for roughly the past two decades of the exoplanet search. The blue bar shows previous planet discoveries, the red bar shows previous Kepler planet discoveries, the gold bar displays the 715 new planets verified by multiplicity.

Image Credit: NASA Ames/SETI/J Rowe

This method can be likened to the behavior we know of lions and lionesses. In our imaginary savannah, the lions are the Kepler stars and the lionesses are the planet candidates. The lionesses would sometimes be observed grouped together whereas lions tend to roam on their own. If you see two lions it could be a lion and a lioness or it could be two lions. But if more than two large felines are gathered, then it is very likely to be a lion and his pride. Thus, through multiplicity the lioness can be reliably identified in much the same way multiple planet candidates can be found around the same star.

"Four years ago, Kepler began a string of announcements of first hundreds, then thousands, of planet candidates --but they were only candidate worlds," said Lissauer. "We've now developed a process to verify multiple planet candidates in bulk to deliver planets wholesale, and have used it to unveil a veritable bonanza of new worlds."

These multiple-planet systems are fertile grounds for studying individual planets and the configuration of planetary neighborhoods. This provides clues to planet formation.

Four of these new planets are less than 2.5 times the size of Earth and orbit in their sun's habitable zone, defined as the range of distance from a star where the surface temperature of an orbiting planet may be suitable for life-giving liquid water.

One of these new habitable zone planets, called Kepler-296f, orbits a star half the size and 5 percent as bright as our sun. Kepler-296f is twice the size of Earth, but scientists do not know whether the planet is a gaseous world, with a thick hydrogen-helium envelope, or it is a water world surrounded by a deep ocean.

"From this study we learn planets in these multi-systems are small and their orbits are flat and circular -- resembling pancakes -- not your classical view of an atom," said Jason Rowe, research scientist at the SETI Institute in Mountain View, Calif., and co-leader of the research. "The more we explore the more we find familiar traces of ourselves amongst the stars that remind us of home."

This latest discovery brings the confirmed count of planets outside our solar system to nearly 1,700. As we continue to reach toward the stars, each discovery brings us one step closer to a more accurate understanding of our place in the galaxy.

Launched in March 2009, Kepler is the first NASA mission to find potentially habitable Earth-size planets. Discoveries include more than 3,600 planet candidates, of which 961 have been verified as bona-fide worlds.

The closest supernova of its kind to be observed in the last few decades has sparked a global observing campaign involving legions of instruments on the ground and in space, including NASA's Spitzer Space Telescope. With its dust-piercing infrared vision, Spitzer brings an important perspective to this effort by peering directly into the heart of the aftermath of the stellar explosion.

The closest supernova of its kind to be observed in the last few decades has sparked a global observing campaign involving legions of instruments on the ground and in space, including NASA's Spitzer Space Telescope.

Image Credit: NASA/JPL-Caltech/Carnegie Institution for Science

Dust in the supernova's host galaxy M82, also called the "Cigar galaxy," partially obscures observations in optical and high-energy forms of light. Spitzer can, therefore, complement all the other observatories taking part in painting a complete portrait of a once-in-a-generation supernova, which was first spotted in M82 on Jan. 21, 2014. A supernova is a tremendous explosion that marks the end of life for some stars.

"At this point in the supernova's evolution, observations in infrared let us look the deepest into the event," said Mansi Kasliwal, Hubble Fellow and Carnegie-Princeton Fellow at the Observatories of the Carnegie Institution for Science and the principal investigator for the Spitzer observations. "Spitzer is really good for bypassing the dust and nailing down what's going on in and around the star system that spawned this supernova."

Supernovas are among the most powerful events in the universe, releasing so much energy that a single outburst can outshine an entire galaxy. The new supernova, dubbed SN 2014J, is of a particular kind known as a Type Ia. This type of supernova results in the complete destruction of a white dwarf star—the small, dense, aged remnant of a typical star like our sun. Two scenarios are theorized to give rise to Type Ia supernovas. First, in a binary star system, a white dwarf gravitationally pulls in matter from its companion star, accruing mass until the white dwarf crosses a critical threshold and blows up. In the second, two white dwarfs in a binary system spiral inward toward each other and eventually collide explosively.

Type Ia supernovas serve a critically important role in gauging the expansion of the universe because they explode with almost exactly the same amount of energy, shining with a near-uniform peak brightness. The fainter a Type Ia supernova looks from our vantage point, the farther away it must be. Accordingly, Type Ia supernovas are referred to as "standard candles," which allow astronomers to pin down the distances to nearby galaxies. Studying SN 2014J will help with understanding the processes behind Type Ia detonations to further refine theoretical models.

Fortuitously, Spitzer had already been scheduled to observe M82 on January 28, a week after students and staff from University College London first spotted SN 2014J on Jan. 21. Subsequent observations, also part of Kasliwal's SPIRITS (SPitzer InfraRed Intensive Transients Survey) program, took place on Feb. 7, 12, 19 and 24 and are slated for March 3.

The supernova is glowing very brightly in the infrared light that Spitzer sees. The telescope was able to observe the supernova before and after it reached its peak brightness. Such early observations with an infrared telescope have only been obtained for a few Type Ia supernovas in the past. Researchers are currently using the data to learn more about how these explosions occur.